全文获取类型
收费全文 | 5591篇 |
免费 | 230篇 |
国内免费 | 21篇 |
专业分类
化学 | 4057篇 |
晶体学 | 20篇 |
力学 | 130篇 |
数学 | 693篇 |
物理学 | 942篇 |
出版年
2023年 | 42篇 |
2022年 | 42篇 |
2021年 | 58篇 |
2020年 | 104篇 |
2019年 | 65篇 |
2018年 | 45篇 |
2017年 | 75篇 |
2016年 | 142篇 |
2015年 | 166篇 |
2014年 | 165篇 |
2013年 | 264篇 |
2012年 | 331篇 |
2011年 | 378篇 |
2010年 | 230篇 |
2009年 | 187篇 |
2008年 | 352篇 |
2007年 | 342篇 |
2006年 | 322篇 |
2005年 | 305篇 |
2004年 | 229篇 |
2003年 | 210篇 |
2002年 | 227篇 |
2001年 | 116篇 |
2000年 | 90篇 |
1999年 | 80篇 |
1998年 | 66篇 |
1997年 | 71篇 |
1996年 | 79篇 |
1995年 | 68篇 |
1994年 | 55篇 |
1993年 | 56篇 |
1992年 | 49篇 |
1991年 | 35篇 |
1990年 | 40篇 |
1989年 | 33篇 |
1988年 | 22篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 37篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1982年 | 35篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 22篇 |
1978年 | 32篇 |
1977年 | 26篇 |
1976年 | 25篇 |
1974年 | 21篇 |
1973年 | 21篇 |
排序方式: 共有5842条查询结果,搜索用时 15 毫秒
991.
Yulia B. Monakhova Svetlana P. Mushtakova Thomas Kuballa Dirk W. Lachenmeier 《Magnetic resonance in chemistry : MRC》2014,52(12):755-759
An eight‐fold suppression pulse sequence was recently developed to improve sensitivity in 1H NMR measurements of alcoholic beverages [Magn. Res. Chem. 2011 (49): 734–739]. To ensure that only one combined hydroxyl peak from water and ethanol appears in the spectrum, adjustment to a certain range of ethanol concentrations was required. To explain this observation, the structure of water–ethanol solutions was studied. Hydroalcoholic solutions showed extreme behavior at 25% vol, 46% vol, and 83% vol ethanol according to 1H NMR experiments. Near‐infrared spectroscopy confirmed the occurrence of four significant compounds (‘individual’ ethanol and water structures as well as two water–ethanol complexes of defined composition – 1 : 1 and 1 : 3). The successful multiple suppression can be achieved for every kind of alcoholic beverage with different alcoholic strengths, when the final ethanol concentration is adjusted to a range between 25% vol and 46% vol (e.g. using dilution or pure ethanol addition). In this optimum region, an individual ethanol peak was not detected, because the ‘individual’ water structure and the 1 : 1 ethanol–water complex predominate. The nature of molecular association in ethanol–water solutions is essential to elucidate NMR method development for measurement of alcoholic beverages. The presented approach can be used to optimize other NMR suppression protocols for binary water–organic solvent mixtures, where hydrogen bonding plays a dominant role. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
992.
993.
994.
FU Yao-Tsung YI YuanPing COROPCEANU Veaceslav RISKO Chad AZIZ Saadullah G. BRDAS Jean-Luc 《中国科学:化学(英文版)》2014,57(10):1330-1339
We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations. 相似文献
995.
996.
997.
Julia Rüger Christopher Timmermann Dr. Alexander Villinger Alexander Hinz Dr. Dirk Hollmann Prof. Dr. Wolfram W. Seidel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11191-11195
The capability of donor‐substituted alkynes to link different metal ions in a side‐on carbon donor‐chelate coordination mode is extended from the donor centers S and P to the second period element N. The complex [Tp′W(CO)2{η2‐C2(S)(NHBn)}] (Tp′=hydrido‐tris(3,5‐dimethylpyrazolyl)borate, Bn=benzyl) bearing a terminal sulfur atom and a secondary amine substituent is accessible by a metal‐template synthesis. Subsequent deprotonation allowed the formation of remarkably stable heterobimetallic complexes with the [(η5‐C5H5)Ru(PPh3)] and the [Ir(ppy)2] moiety. Electrochemical and spectroscopic investigations (cyclic voltammetry, IR, UV/Vis, luminescence, EPR), as well as DFT calculations, and X‐ray structure determinations of the W–Ru complex in two oxidation states reveal a strong metal–metal coupling but also a limited delocalization of excited states. 相似文献
998.
Alexandru Vlasceanu Dr. Søren L. Broman Anne S. Hansen Anders B. Skov Prof. Dr. Martina Cacciarini Prof. Dr. Anders Kadziola Prof. Dr. Henrik G. Kjaergaard Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10796-10800
The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA–DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF–VHF). A stepwise energy release over two sequential ring‐closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long‐term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release. 相似文献
999.
David Bialas Christoph Brüning Dr. Felix Schlosser Dr. Benjamin Fimmel Johannes Thein Prof. Dr. Volker Engel Prof. Dr. Frank Würthner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):15011-15018
The optical properties of a series of three cyclophanes comprising either identical or different perylene bisimide (PBI) chromophores were studied by UV/Vis absorption spectroscopy and their distinctive spectral features were analyzed. All the investigated cyclophanes show significantly different absorption features with respect to the corresponding constituent PBI monomers indicating strong coupling interactions between the PBI units within the cyclophanes. DFT calculations suggest a π‐stacked arrangement of the PBI units at close van der Waals distance in the cyclophanes with rotational displacement. Simulations of the absorption spectra based on time‐dependent quantum mechanics properly reproduced the experimental spectra, revealing exciton‐vibrational coupling between the chromophores both in homo‐ and heterodimer stacks. The PBI cyclophane comprising two different PBI chromophores represents the first example of a PBI heterodimer stack for which the exciton coupling has been investigated. The quantum dynamics analysis reveals that exciton coupling in heteroaggregates is indeed of similar strength as for homoaggregates. 相似文献